The present invention relates to a beverage containing a soybean protein and a process for producing the same.
Soybeans are an excellent food in view of a protein nutritional source. A beverage is one of the desired forms for ingesting this protein. However, the use of a beverage for this purpose is limited because soybean milk forms a precipitate at a weak acidic region where high storage stability can be expected, while a generally acceptable taste can hardly be obtained at a neutral pH region. On the other hand, an acidic beverage comprising as a main ingredient a soybean protein isolate obtained from a soybean has a problem that the beverage has unsatisfactory drinkability, because a soybean protein isolate has a unique unpleasant smell or taste, and is liable to form an aggregate or precipitate at an acidic pH region, thereby requiring addition of a dispersant or stabilizer such as a polysaccharide, etc, for dispersing such an aggregate or precipitate, which results in increase in viscosity.
Heretofore, many methods have been proposed to fractionate β-conglycinin, which is one of main constituent components of a soybean protein, from a soybean protein. For example, in addition to experimental fractionation methods by Wolf, et al, Tang, et at, and Nagano et al, as well as a method of Wu et al (JAOCS, vol. 76, No. 3, p 285-293 (1999)) which is said to be industrialization of the above method of Nagano et al (J. Agric. Food Chem., vol. 40, p 941-944 (1992)), there are methods disclosed by JP 48-56843 A, JP 49-31843 A, JP 51-86149 A, JP 55-124457 A, JP 55-153562 A, JP 56-64755 A, JP 57-132844 A, JP 58-36345 A, JP 61-187755 A, etc.
U.S. Pat. No. 6,171,640 discloses the isolation of a protein from a soybean which is derived by breeding technique and has a high β-conglycinin content, the use of the isolated protein in the production of beverages or beverage powders, and the like.
Further, a soybean contains about 2% of phytic acid and it has been known that a soybean protein inclusive β-conglycinin forms a complex with phytic acid, which inhibits digestibility of the soybean protein (Liter et al, J. Food Sci., 52, 325, 1987). Furthermore, Yoshida et al (JP 2000-245340 A) reports that phosphate compounds inclusive such phytic acid cause unpleasant “heavy feeling” of the stomach and decomposition and removal of these phosphate compounds alleviate this unpleasant “heavy feeling” to improve drinkability of a soybean protein beverage.